One giant river prawn looks pretty much like any other giant river prawn.

But there's a big difference between male and female prawns. Male prawns can grow faster - and up to 60 percent larger - than females.

And that can make a big difference for shrimp farmers. The giant river prawn, Macrobrachium rosenbergii, is one of the world's most cultivated and consumed freshwater shrimp.

Making more males

A team of researchers at Israel's Ben Gurion University of the Negev is using a ground-breaking method - called temporal gene silencing through RNA Interference - to get the huge crustaceans to give birth to only males.

That will help farmers, says Professor Amir Sagi, who developed the technology and is leading the team. "So if the end user, the grower, in India or in Vietnam or in China will grow those, he will have something like 60 percent increase in his income."

Another advantage of the new technique is safety.

"We do not have to use any chemicals nor any hormones and it is a non-GMO," Sagi explained, so "it is not genetically modifying the organism."

Transsexual shrimp

The method involves carefully injecting female prawns with a molecule that silences a gene, turning it into a male. These transsexual prawns can still mate with regular males, but all their offspring will be male.

Sagi says expert workers can inject about 2,000 prawns a day, with each individual able to produce thousands of eggs over several cycles.

The sex change occurs only in the animals that have been injected and does not affect subsequent generations.

The technique is currently being used to help farmers in Asia, and according to Sagi, has unlimited potential for future applications in the fields of marine and fresh water agriculture.